Thermionic device



y 1929. H. J. ROUND 0 1,711,969

THERMIONIC DEVICE Filed May 2. 1922 Fly? Fig 3 Fig. 1

Umjowf [arm/7f //7,01// 3 E 00/,60/ lwmm HENRY JOSE PH ROUND izy 41MPatented May 7, 1929.

s 1,711,96il

UNITED STATES, PATENT oFFica' HENRY JOSEPH ROUND, LONDON, ENGLAND,ASSIGNOR TO RADIOCORPORATION' OF AMERICA, A CORIORATION DELAWARE.

THEBMIONIC DEVICE.

Application filed May 2, 1922, Sieria1 No. 557,918, and in Great BritainMay 18, 1921.

It is well known that the relation between the space current and thevoltage applied to a thermionic device or vacuum tube is usually notlinear and is at the best never linearover more than a very small-range.

7 It has been shown that in a vacuum tube of should'be of the linearform i=7cV over a large range. This is particularly so when a threeelectrode tube is used for voice magnification; Also when a two or threeelectrode valve is used in combination with an independent oscillator asinthe well knownheterodyne method, it is advisable to use a rectifierwhich has this straight line law sothat isig nals appearingsimultaneously do not tend to distort one another, and when a, threeelectrode tube is used for the introduction of negative resistance inthe well known way a straight line lawis desirable. Also when a valvecircuit is arranged to give a certain frequency of oscillations,straight line laws of the characteristic of both anode and'grid circuitsare desirable.

According to this invention there is'introduced into the anode circuitof a tube a resistance which is large compared with the resistance ofthe tube so that the voltage current relation of this combined system ismainly controlled by the resistance, and then, since the slope of thecharacteristic is very much less,'severalof these tube resistancesystems are arranged in parallel so that the characteristic of the wholecombination is given any required slope.

Both theoretically and experimentally it is found that the result is acharacteristic which has its curvature reduced in proportion tothenumber of tubes used and to the resistance placed in series with eachtube, the larger the resistance, and the greater the number of tubes,the straighter the characteristic.

Such a combination can be then used as a unit just as one tube is used.

In some cases the anodes of two or more tubes may be connected-to asingle resistance if the characteristics of such tubes are the same.

In some cases also a resistance of high value may be inserted into thegrid circuit of a three electrode tube in addition to the resistance inthe anode circuit. i

' My invention is illustrated by the .acc'om:

panying drawings, in which: I

Fig. 1 1s a series of curves showing the rider tion between inputvoltage and out-put current. I

' Fig. 2 is a diagram of an arrangement in accordance with my invention,and Fig. 3 is a modification' f i V Figs.-4 .and 5, are diagrammaticrepresentai tions of circuits embodying the invention for certainpurposes; v 1

In Figure l curve Arepresents thee-harm teristic of a two electrodevalve, and curve (B represents the characteristic of a resistance. Bymerely adding thevoltages at equal currents we get the characteristic Cofthe series coinbin'ation'of thevalve and resistance which isoffliessslopethan either curve A or curve B,

and byinultiplying,all; ordinates by three we get,thecharacteristic'oithree of these combinations in parallel, noticeably a longer andstralghter curve than the original single valve arrangement. i

The arrangement is shown in Figure 2 where V, V, are three diodes or twoelectrode devices arranged in parallel with a resistance R in series"with the anode of each.

It is obvious that if all the three valves are exactly similar incharacteristics the result is equally well obtained by the arrangementshown in Figure 3 where the one resistance R is equal to one-third ofany of the resistances Rin Figure 2.

A much longer and straighter characteristic still can be obtained byusing more valves in parallel with high resistances in series with each.

No modification of this arrangement need be made if the diodes bereplaced by'triodes istic similar to that of a French standard receivingvalve and with 150,000 ohmsin series with it may be arranged inparallel. The result is a characteristic which has about the same slopeas the one valve at its best but this slope is maintained with about onetwelfth the curvature for twelve times the length.

"Such an arrangement may be employed for the magnification of voicecurrents asshown in Figure 4c, in which the inputtelephone is coupledthrough transformer T to the parallel connected grids of the five valvesV Resistances R are connected in series with each of the anodes of thevalves, and an output transformer T is connected to the tubes which arein parallel. As shown in Fig. 5, the arrangement may be used as aconstant wave length heterodyne, or as a reaction cir' cuit of lowdamping acting as a filter between input and output circuits. Thearrangement comprises a plurality of three electrode tubes V havingresistances R connected as in Fig. 2. The input circuit is coupled to anoscillatory circuit 0 which is also coupled to the out-put circuit. Theinput circuit of the valves is connected across the condenser of theoscillatory circuit and the output circuit of the valves is coupledthrough coil P to the inductance of the oscillatory circuit forming a reenerative or feed back circuit. This circuit may act as a heterodyne ora reaction circuit depending on the adjustment of the coupling toproduce amplification or generation of oscillations. In this case highresistances R are inserted in series with the "grids. In paralleling alarge number of valves for transmission it is advantageous to introducethese separate resistances and the larger the number of valves, thegreater these resistances can be Without the overall loss reducing theefiiciency seriously, providing the valves are made to stand highvoltages.

Having described my invention, what I claim is:

1. Amplifying means for incoming electrical cnerg comprising a pluralityof three electrode thermionic devices in parallel, each of said deviceshaving input and output sides, individual means in each of said outputsfor accentuating the linear characteristics of said devices when used incombination, said means also serving to equalize the operatingcharacteristics of said devices, and means in said output circuit i'orai'lecting each of said devices equally in accordance with said incomingenergy.

2. Means for controlling the flow ofelec trical energy in circuit,comprisin a plurality of parallel paths each of which'contains anelectron discharge device, means for equally varying the conductivity ofeach of said devices in accordance with said flow, and means in theanode circuit of each of saiddevices for accentuating and equalizing thelinear characteristics of said devices when used in combination. g

I 3: Amplifying means for electrical energy, comprising a plurality ofthermionic devices connected in parallel, and individual means in theanode circuit of each of said devices for equalizing the constants ofsaid devices and accentuating the linear characteristics thereof whenused in combination.

HENRY Josiirn ROUND. i

